Photosensitive compositions including a polyimide/polyimide precursor (or polyamic acid) have been widely used to form polymer relief patterns serving as insulation or passivation films for very large scale integration (VLSI) and multichip modules (MCM) because polyimides have excellent properties especially in terms of thermal stability and chemical resistance. Conventionally, the photosensitive compositions include a photosensitive additive, which serves to control the dissolution rate of the composition into an alkaline developer solution. The dissolution rate into the developer solution can be differentiated between the exposed region and the non-exposed region, thereby allowing development of a pattern. The developed pattern is subjected to an appropriate thermal process to form a relief pattern.
In the case of conventional polyimides used in photosensitive compositions, the polyimide includes alkaline soluble groups. However, once the photosensitive compositions are formed into a relief pattern, those alkaline soluble groups should be removed because they can negatively impact the desired physiochemical properties of the polyimide relief pattern. For example, the presence of such alkaline soluble groups can result in higher water absorbance and higher dielectric constants than in a similar polymer without such groups. In order to remove the alkaline soluble groups, the developed pattern generally has to be heated at a high temperature, e.g., at 320° C. or more.
Thus, one objective of the present invention is to provide a photosensitive composition including a polyimide, which can be formed into a relief pattern at a lower temperature. Another objective is to provide a photosensitive composition including a polyimide, whose alkaline soluble groups can be removed after developing a polyimide pattern at a lower temperature. A further objective of the present invention is to provide a photosensitive composition including a polyimide precursor, whose alkaline soluble groups can be removed after developing a polyimide pattern at a lower temperature.